[External] Re: openstack volume snapshots and deleting

Sean McGinnis sean.mcginnis at gmx.com
Thu Dec 5 18:58:47 UTC 2019

On Thu, Dec 05, 2019 at 06:25:28PM +0000, Ratliff, John wrote:
> Yes, I  tried this second thing, but it doesn't work either.
> I created a new instance called test1.example.net.
> I created a volume snapshot (test1.example.net_ss1)
> I created a volume from that snapshot (vol_from_ss)
> I created a volume from the volume that was from the snapshot
> (vol_from_vol_from_ss)
> I deleted the vol_from_ss (this works)
> I deleted the snapshot (this does not work)

Looking at the RBD driver, it looks like it does not actually follow the
expected clone semantics. Unless rbd_max_clone is set to 0, or the number of
clones is less than whatever that is set to, it will actually do a COW volume
on top of the snapshot.

This is a performance optimization (it doesn't have to copy all of the data
into the new volume), but is actually a bug, IMO.

You can try changing that config option and restarting services to pick that
up, then trying again.

Otherwise, it looks like that drivers clone handling will create its own
snapshot of a volume. So unless you need to keep that snapshot around for some
other reason, it looks like you should be able to just:

openstack volume create --source orig-volume new-volume

And if I follow it right, it will create a snapshot under the covers, then use
that to create the new volume.

Hopefully one of those helps.


More information about the openstack-discuss mailing list